Blekki Stone

“Stinking Sinking Shrinking Goo,
Hard when Hell is frozen through,
Never skip a stone so blue,
‘Cuz Blekki Stones will stick to you!”

-Icewind Dale childrens’ nursery rhyme

Blekki “Stones” are the black (blue?) sheep of the ooze family, sticking (DC 18 STR) to whatever warms them and taking 1d4 rounds to reform as a Gelatinous Cube around their victim.